This invention relates to novel polymerizable imidazolidinone monomers, their preparation, and their use to form self-crosslinking polymers which are thermosettable without the release of formaldehyde. It also relates to the use of such polymers in emulsion form as nonwoven binders.
It is well-known in the art to employ self-crosslinking polymers, either in emulsion or solution form, as coatings, binders, or adhesives for a variety of substrates. Self-crosslinking polymers are distinguished from crosslinkable polymers in that the latter contain a functionality, such as a carboxyl group, which can only be crosslinked by the addition of a co-reactant (i.e., crosslinker) to the polymer emulsion or solution. A typical crosslinkable system can be represented as follows: ##STR4##
In contrast, self-crosslinking polymers contain a functionality which is self-reactive and consequently do not require the use of a coreactant species per se. A typical self-crosslinking system can be represented as follows: ##STR5##
The advantages of the self-crosslinking polymer systems are their simplicity, economy, and particularly their efficiency. Such systems have been used as textile adhesives, non-woven binders, pigment binders for glass fabrics, and fabric finishing agents for hand and weight modification. On curing, such systems produce textile products with excellent durability to washing and dry cleaning. They have also been used in pigment printing and dyeing and as a binder for paper.
Both the self-crosslinking and crosslinkable polymer systems of the prior art suffer from the disadvantage that toxic free formaldehyde is present either during the curing or the preparation of the polymers. The self-crosslinking systems, which are typically formaldehyde-amide polymeric adducts containing methylolacrylamide repeating units, liberate formaldehyde during curing of the crosslinked thermoset polymer. The crosslinkable systems, which are typically based on urea-formaldehyde or melamine-formaldehyde resins and crosslinkers, may contain residual free formaldehyde.
In addition to the odor problems created by the presence of free formaldehyde, the dermatitic effect is a serious problem. The exposure of operating personnel and cosumers to formaldehyde has been a recent concern of both industry and regulatory agencies. This has lead to the search for formaldehyde-free systems, especially self-crosslinking, formaldehyde-free systems for use as nonwoven binders.